<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8" />
		<title></title>
		<style type="text/css">
			@keyframes changeW{
				10%{
					width: 150px;
					background: green;
					
				}
				50%{
					width: 200px;
					background: red;
				}
				100%{
					width: 500px;
					background: pink;
				}
			}
			.box{
				width: 100px;
				height: 100px;
				margin: 300px auto;
				background: #ccc;
				animation: changeW 3s infinite;
			}
		</style>
	</head>
	<body>
		<div class="box">
			
		</div>
	</body>
</html>
